The most intriging routines are $e686 and $e6ce. The weirdest part are the "bind" and "unbind" sequences. Withoug theses the storage area for the boxes is unreachable. It looks like the small sequence that needs to be written to $1807 before accessing the BRAM. This also explains when dumped the area $80000 (rom bank $40) is empty (filled with $ff).